Wireless communication systems are being widely deployed in order to provide various kinds of communication services, such as voice or data. In general, a wireless communication system is a multiple access system which can support communication with multiple users by sharing available radio resources (bandwidth, transmission power, etc.). The multiple access systems may include, for example, a Time Division Multiple Access (TDMA) system, a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, and a Single Carrier Frequency Division Multiple Access (SC-FDMA) system.
The IEEE (Institute of Electrical and Electronics Engineers) 802.16 standard provides technologies and protocols for supporting broadband wireless access. IEEE 802.16-2001 had been standardized since 1999 and was approved in 2001. The IEEE 802.16-2001 is based on a single carrier physical layer called ‘WirelessMAN-SC.’ In the IEEE 802.16a standard approved in 2003, ‘WirelessMAN-OFDM’ and ‘WirelessMAN-OFDMA’ other than ‘WirelessMAN-SC’ were further added to the physical layer. After the IEEE 802.16a standard was completed, a revised IEEE 802.16-2004 standard was approved in 2004. In order to modify bugs and error of the IEEE 802.16-2004 standard, IEEE 802.16-2004/Cor1 was completed in 2005 in the form of ‘corrigendum.’ A standard specification based on the IEEE 802.16-2004/Cor1 is called IEEE 802.16e or WiMAX.
Today, in the IEEE 802.16 Broadband Wireless Access Working Group, the standardization of an IEEE 802.16m standard (i.e., a new technology standard) is being performed on the basis of the IEEE 802.16e. The IEEE 802.16m standard requires supporting flexibly not only new systems, but the existing IEEE 802.16e standard. The IEEE 802.16m system is based on TDD. That is, uplink transmission and downlink transmission are performed in the same frequency band at different point of times.
As a variety of wireless communication systems are deployed, coexistence between heterogeneous systems becomes problematic. In other words, heterogeneous systems provide services in the same region and time. In particular, in order for heterogeneous TDD systems to coexist, it is important that downlink transmission and uplink transmission are not performed at the same time. If downlink transmission and uplink transmission overlap with each other between the heterogeneous TDD systems, data loss may occur because of interference.